A speaker is a device that converts an electrical signal into a sound signal. The speaker has a structure in which a bobbin having a voice coil wound therearound is inserted into a magnetic circuit having a magnet, a plate and a yoke, so that the bobbin and a diaphragm connected to the bobbin are vibrated by the magnetic force generated in the magnetic circuit, thereby outputting sounds.
Hereinafter, a conventional speaker will be described in detail with reference to the drawing.
FIG. 1 is a sectional view of a conventional speaker.
As shown in FIG. 1, the conventional speaker is provided with a base frame 10 formed to a thickness of about 1.0 to 1.2 mm using iron (Fe) or synthetic resin. A magnetic circuit part 20 generating a magnetic force is coupled to the base frame 10 at the bottom side of the base frame 10, and a vibration part 30 generating an electric force is mounted in the inside of the base frame 10.
The magnetic circuit part 20 comprises a ring-shaped plate 21, a ring-shaped magnet 23 and a yoke 25. Here, the plate 21 is coupled to the bottom of the base frame 10, and the magnet 23 is coupled to the bottom of the plate 21. The yoke 25 has a support plate 25a coupled to the bottom of the magnet 23 and a pole 25b passing upward through the inside of the magnet 23 and the plate 21.
The vibration part 30 comprises a diaphragm 31, a bobbin 33 and a damper 35. Here, the diaphragm 31 has an edge side coupled to the top side of the base frame 10. The bobbin 33 is formed in the shape of a cylinder having a voice coil wound around an outer circumferential surface thereof so that the upper side of the bobbin 33 is coupled to the diaphragm 31 and the lower side of the bobbin 33 is inserted between the plate 21 and the pole 25b. The damper 35 has an outer circumferential surface coupled to the base frame 10 and an inner circumferential surface coupled to the bobbin 33. In this case, the damper 35 functions to guide the bobbin 33 to be vibrated in a certain direction so that the bobbin 33 is not vibrated in the horizontal direction but vibrated in the vertical direction.
If external power is supplied to the voice coil, the bobbin is vertically vibrated by an action between the magnetic circuit 20 and the voice coil wound around the bobbin 33, and therefore, sounds are generated by vibrating the diaphragm 31.
However, in the conventional speak configured as described above, the inner circumferential surface of the damper 35 should be coupled to the bobbin 33 at a point lower than the diaphragm 31 so that the diaphragm 31 and the damper 35 are not interfered with each other when the bobbin 33 is vertically vibrated. The diaphragm 31 is extended to slope in such a way that the height of the outside edge is greater than that of the inside edge. Hence, there is a structural limitation in implementing the slimness of products, i.e., in decreasing the entire height of the product.
Accordingly, there has been proposed a planar speaker in which a diaphragm is extended in the horizontal direction for the purpose of manufacturing slimline products. However, if the diaphragm is formed in the shape of a horizontal flat plate, deformation such as warp may easily occur when the diaphragm is vibrated. In order to solve such a problem, a planar diaphragm may be bent to increase the strength of the diaphragm or may be formed using a diaphragm material of which the thickness is thick. In this case, the entire thickness of the diaphragm is increased by the thickness of the bent diaphragm or diaphragm material. Therefore, it is difficult to manufacture a speaker suitable for middle/low tone, high power and high sound quality while being thin in thickness.